1. Field of the Invention
The present disclosure generally relates to semiconductor manufacturing processes. More specifically, the present disclosure relates to a band pass filter for radiation in a photo lithography tool.
2. Description of Related Art
Integrated circuits (ICs), such as microprocessors and memory devices, include millions of interconnected semiconductor components such as transistors and capacitors. Sizes of these components have decreased over time to reduce cost of manufacturing, provide additional capabilities, and/or reduce power consumption. Solutions for manufacturing components at smaller sizes focuses on producing smaller feature sizes during photo lithography. Conventionally, in photo lithography, a light source illuminates a mask containing patterns that build the components. Optics reduce the patterns to the desired size, which illuminate a photosensitive material deposited on material stacks that are later processed into semiconductor components.
A minimum feature size produced by a photo lithography process is related, by the Raleigh equation, to k1λ/NA, where k1 is a process dependant variable, λ is the wavelength of the light source, and NA is the numerical aperture of the projection lens. Conventional light sources include an ArF laser, which produces ultraviolet (UV) light with a wavelength of 193 nm. Tools with ArF laser light sources manufacture ICs with feature sizes of 65 nm and 45 nm. One proposal for further reducing feature size includes tools having an extreme ultraviolet (EUV) light source, at a wavelength of approximately 13.5 nm, and therefore a higher resolution capable of imaging smaller features.
Light sources, such as EUV sources, produce additional out-of-band (OOB) radiation at wavelengths outside the desired wavelength for lithography. Specifically, light sources may produce infrared (IR) radiation. IR radiation propagates through the exposure tool heating components in the IC manufacturing process. Heating of components may result in shorter lifespan of the components. Shorter lifespan of lithography tools leads to undesirable costs for the manufacturer, as lithography tools often cost tens of millions of dollars. Additionally, the IR radiation may heat masks used during exposure resulting in damage to the masks or lower achievable resolutions of a lithography tool by reducing the contrast of the images coming off of the mask.